1. Field of the Invention
The presently disclosed subject matter relates to an image pickup apparatus and an image pickup element configured to include a plurality of pixels that share a specific circuit element, and a method for correcting a sensitivity difference.
2. Description of the Related Art
An image pickup element made of a CMOS (complementary metal oxide semiconductor) is low in power consumption and is used for various kinds of portable image pickup apparatuses such as digital cameras and mobile phones.
In the CMOS image pickup element, a technology that a plurality of pixels share one amplifier is widely used as a technology for reducing a number of transistors necessary on a substrate (see Japanese Patent Application Laid-Open No. 2011-086888 and Japanese Patent Application Laid-Open No. 2006-054276).
A sharing configuration in which four pixels of 2×2 pixel arrangement share one amplifier is heavily used because the configuration is particularly well matched with the color filters arranged according to the Bayer array and also because an amplifier can be arranged at the center of four pixels and read gates for the respective pixels can be arranged around the pixels.
Further, Japanese Patent Application Laid-Open No. 2000-308080 discloses an image pickup element configured to employ a three-color random arrangement which satisfies an array restriction condition that an arbitrary target pixel should be adjacent to pixels of three colors including the color of the target pixel, on one of four sides of the target pixel.